The Vietcong's army fought with the guerrilla war tactics.

Guerrilla warfare is irregular warfare, conflicts in which a small group or army uses military tactics, like ambushes and raids, to harass a larger and less-mobile traditional army. The term means "little war" in Spanish, and the word, guerrilla, has been used to describe the concept since the 18th century, and perhaps earlier. Guerrilla warfare describes a conflict between armed civilians and a regular army, either foreign or domestic, where the armed civilians use tactics such as ambush, sabotage, the element of surprise, and extraordinary mobility to strike a vulnerable target and withdraw almost immediately.